During the second debate of the 2012 Presidential campaign, Mitt Romney repeated the frequently levelled Republican charge that it had taken Barack Obama many days to refer to the attack upon the U.S. Embassy in Benghazi as terrorism. Obama disputed that, and the two men argued back and forth until the moderator, Candy Crowley, intervened to say that the President had in fact referred to the incident as an “act of terror” the day after it happened. In the ensuing partisan scrum, conservatives and liberals debated the nuances between an “act of terror” and “terrorism,” proper. Beneath this philological fracas lay a truth evident to political speechwriters, eulogists, and news anchors: in times of tragedy, language matters.

The Charleston police were quick to label what happened in the sanctuary of Emanuel African Methodist Episcopal Church last Wednesday night a “hate crime.” Many crimes are motivated by hatred, yet we reserve the term “hate crime” for an act motivated by an animus that has been extrapolated beyond any single individual and applied to an entire segment of the populace. The murder of nine black churchgoers during Bible study is an act so heinous as to be immediately recognizable as a hate crime. But it was not simply this. We should, for all the worst reasons, be adept by now at recognizing terrorism when we see it, and what happened in Charleston was nothing less than an act of terror.

Yet the term was missing from early descriptions of the incident. Senator Lindsey Graham, of South Carolina, in his initial assessment, said, “I just think he was one of these whacked-out kids. I don’t think it’s anything broader than that.” On Thursday, Governor Nikki Haley posted a statement on Facebook noting that “while we do not yet know all of the details, we do know that we’ll never understand what motivates anyone to enter one of our places of worship and take the life of another.” As a matter of morality, the actions of Dylann Roof, who confessed to the murders, may be a conundrum, but his motivations are far from inscrutable.

The Patriot Act defines “domestic terrorism” as activities that:

(A) involve acts dangerous to human life that are a violation of the criminal laws of the United States or of any State; (B) appear to be intended—(i) to intimidate or coerce a civilian population; (ii) to influence the policy of a government by intimidation or coercion; or (iii) to affect the conduct of a government by mass destruction, assassination, or kidnapping; and (C) occur primarily within the territorial jurisdiction of the United States.

At a minimum, the murders were intended to intimidate and coerce the black civilian population of Charleston, and beyond. A friend of Roof’s said that he had talked about wanting to start a “race war”—something that Roof also reportedly confessed to investigators. And he apparently based his acts on vintage rationalizations for terrorist violence in American history. ...